An internal combustion engine does not exhibit a constant high level of efficiency throughout its operating range. Each engine, and particularly each diesel engine, has an area in its torque vs. speed map where it operates most efficiently. This area can be called the “sweet spot”. For heavy vehicles, such as over-the-highway tractors and trucks, the driving habits that result in operating the engine with maximum or near-maximum efficiency, in the sweet spot, are not readily apparent to the driver. Parameters affecting engine efficiency include but are not limited to engine speed, engine load, engine temperature, ambient temperature, and ambient air pressure.
Some systems provide drivers with information on vehicle performance and optimum operating point, but these systems typically may indicate only that the engine is in the sweet spot and do not indicate the changes needed to get to this favorable operating range. Without such feedback, drivers have to rely on experience and “feel”, which inevitably results in less than optimal operating efficiency.
WO 03/76788 A1 by Edwards discloses a gas substitution system for a dual-fuel (diesel/liquefied petroleum gas) diesel engine that monitors load and RPM and the operational state of the engine and vehicle, including throttle displacement, cruise control, idle, wheel and engine braking, and manual control. Data is collected to establish parameters such as fuel consumption and exhaust emissions for load/RPM pair values and used to create a table of optimum gas substitution values at each load/RPM pair within the range of operational states within which substitution is viable. This arrangement does not interact with and provide feedback to the driver in real time.
WO 82/02576 describes using a microprocessor to monitor a number of vehicle operating parameters that can be displayed, for example on a light-emitting diode (LED). A keypad may be used to input other vehicle-related parameters. In addition to presenting torque, RPM, speed, etc. values, the display can change color to indicate a recommended gear change to the driver. Nevertheless, this is just a method of realizing variable compression ratio and is not a driving aid.
EP 0 919 419 A1 by Trepp discloses a remote cooperative engine control system with remote data processing in which recommended control signals may be communicated to drivers of many vehicles, either from the engine control systems or from a remote location. A display for standard vehicle data (speed, mileage, fuel) may be used for this purpose. Engine operating characteristics may be altered, for example, based upon ambient conditions (temperature, level of oxides, etc).
U.S. Pat. No. 4,383,514 to Fiala describes an arrangement for fuel supply to the combustion chambers of an engine. Fuel economy can be improved by isolating (i.e., not fueling) certain combustion chambers based upon the load on the engine. For example, fuel may be supplied to four combustion chambers under heavy load, to only two chambers under reduced load, and to no chambers under braking.
U.S. Pat. No. 4,559,599 to Habu et al. describes a shift indication apparatus, including a shift up/down indicator, based on a stored torque data map and a stored fuel consumption rate data map of an engine. Economical running of the vehicle may be realized by obeying the shift indicator.
U.S. Pat. No. 5,017,916 to Londt et al. discloses a shift prompter/information display system for indicating gear shift timing and other related data to a driver. A section of the display can indicate a target value for fuel economy when the vehicle is in a cruising mode. A target gear to which the transmission should be shifted is displayed when the engine speed is equal to the synchronous meshing speed of the target gear.
U.S. Pat. No. 6,067,847 to Staerzl discloses a running quality evaluator for an engine that allows a technician to monitor the running engine on a display and to make corrections for optimizing the engine function. Engine operating parameters such as spark timing can be adjusted to improve quality. The arrangement quantifies the running performance and outputs a signal that can be interpreted as an indicator of performance quality.
U.S. Pat. No. 6,178,373 to Davis et al. describes an engine control method that involves generating optimized control set points for fuel flow, airflow, exhaust gas recirculation, and spark ignition timing to balance emissions and fuel economy.
U.S. Pat. No. 6,356,831 to Michelini et al. relates to optimizing gear shifting performance in a manual transmission of an internal combustion engine and more particularly to optimizing gear shifting performance with a lean-capable engine that can operate in multiple combustion modes. An operator is given “shift up” and “shift down” indications on a shift schedule based on lowest cost value for fuel economy and vehicle emissions as a function of different engine combustion modes.
These devices and systems do not provide enough feedback to drivers, which forces drivers to rely on experience and “feel”. Drivers also have no benchmark from which operating performance can be improved.